The invention relates to an operating device for the cover of a sliding and lifting sunroof of a motor vehicle of the type having desired value and actual value transmitters for the sliding function and for the lifting roof function as well as with an actuator that is part of a control circuit by which the desired value signal that is supplied by the desired value transmitter, and that corresponds to the desired position of the cover selected in each case, is compared with a respective actual value signal, that corresponds to the actual position of the cover, so as to cause the actual cover position to be adjusted until its positional deviation from that desired has become zero.
In a known operating device of this kind (U.S. Pat. No. 4,556,835), the operating element of the desired value transmitter is a potentiometer that is set by a control knob or a sliding lever and can be adjusted between two end positions, e.g., from fully lifted to fully retracted, by turning or sliding thereof through a reference intermediate position that corresponds to a zero position of the roof, e.g., the closed roof position. The turning or sliding of the operating element between the one end position and the reference intermediate position controls the sliding function, while the lifting roof function is controlled by turning or sliding the operating element between the reference intermediate point and the other end position. The stationary display symbols assigned to the adjustable operating element indicate to the user the direction in which the operating element is to be adjusted for the respective, desired movement. However, in adjusting the operating element, there exists a certain danger that, by watching the operating element and the associated display symbols, the attention of the driver is diverted from driving events.
It is also known (U.S. Pat. No. 4,600,237), in controlling the movement of a sliding and lifting sunroof, to provide a switch with an operating element that is supported to have a swinging movement to activate the lifting roof function, and is supported to slide to activate the sliding sunroof operation. However, such a switch is, basically, unsuited as a desired value transmitter for a servomechanism of the type developed according to the invention. That is, for such a switch (which opens and closes one or more circuits, instead of producing a variable signal) to be usable in place of a desired value transmitter, for example, as is used in U.S. Pat. No. 4,556,835, a switch of the type disclosed would require as many stationary switch contacts as thereare positions into which the cover can be moved. Thus, while it may be theoretically possible to emulate the operation of a variable signal transmitter via a multiple contact switch, in practice it would not be feasible to provide, perhaps, for more than one or two intermediate positions to be produced in addition to the end positions of travel. This result is because the switch would become too complicated and too bulky to allow installation in the restricted space available in a typical car, should a large number of stationary switch contacts (for example, 50) have to be provided, as would be necessary to approach the infinitely variable position control capabilities obtainable by a desired value transmitter, such as one utilizing a potentiometer.